Mobile communication equipment, e.g., cellular telephones, mobile modems, and the like, provide communication services to end-users by interacting with a communication network via a radio link. Depending on the protocol or standard used for the radio link, the mobile communication equipment may be referred to as a mobile device, mobile terminal, mobile station, or as user equipment (“UE”). For example, the standards for Global System for Mobile Communications (“GSM”) usually refer to the mobile communication equipment as the “mobile station,” whereas the standards for Universal Mobile Telecommunication System (“UMTS”) usually refer to the mobile communication equipment as the “user equipment.” This disclosure uses the term “user equipment” (or “UE” for short) to refer to all forms of mobile communication equipment, including devices traditionally referred to by the term “user equipment,” as well as mobile communication equipment traditionally referred to by other terms.
It is useful to be able to estimate the location of a UE. For example, some jurisdictions require service providers to locate user equipment during an emergency (“E-911”). Many UE devices incorporate a Global Positioning Satellite (“GPS”) receiver and can use GPS signals to pinpoint its location. However, GPS location data is not always available. For example, the satellite signals may be obstructed or the GPS receiver may be disabled, e.g., to conserve power. When a UE cannot report its location based on GPS, other methods are needed to estimate the UE's location. Estimating a location of a UE is known as “positioning.” While precise positioning is desirable, e.g., using GPS, the ability to position a UE to within even a reasonably-sized geographic area can still be helpful, e.g., for locating a UE in an emergency.
User equipment interacts with the communication network via a radio link between the UE and a network access node that includes one or more antennas, transceivers, and computer controllers. The discrete elements of the network access node may include, for example, various antenna structures for omnidirectional or directed antennas, radio transceivers (“TRX”), a base transceiver station (“BTS,” also called a “Node B,” “Evolved Node B,” or “eNodeB,” depending on the implemented protocol or standard), amplifiers, controllers, and so forth. For simplicity, the network access node is referred to herein as a “base station” without limitation to any particular form or type of network access node.
If a UE is in communication with a particular base station, then the location of the UE is somewhere within the coverage area of the base station. In some settings, a network service provider will maintain multiple base stations covering a geographic area. When a UE is within range of multiple base stations, it is possible to narrow the possible location of the UE based on the locations of the base stations.
However, typical positioning methods require multiple base stations at fixed locations. These methods do not work when the UE is interacting with a single base station that is in motion.